[PATCH 3/4] PCI: dw-rockchip: Add L1sub support

[Shawn Lin <shawn.lin@rock-chips.com>]

The driver should set app_clk_req_n(clkreq ready) of PCIE_CLIENT_POWER reg
to support L1sub. Otherwise, unset app_clk_req_n and pull down CLKREQ#.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
---
 drivers/pci/controller/dwc/pcie-dw-rockchip.c | 31 ++++++++++++++-----
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
index 87dd2dd188b4..8a52ff73ec46 100644
--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
+++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
@@ -62,6 +62,12 @@
 /* Interrupt Mask Register Related to Miscellaneous Operation */
 #define PCIE_CLIENT_INTR_MASK_MISC	0x24
 
+/* Power Management Control Register */
+#define PCIE_CLIENT_POWER		0x2c
+#define  PCIE_CLKREQ_READY		0x10001
+#define  PCIE_CLKREQ_NOT_READY		0x10000
+#define  PCIE_CLKREQ_PULL_DOWN		0x30001000
+
 /* Hot Reset Control Register */
 #define PCIE_CLIENT_HOT_RESET_CTRL	0x180
 #define  PCIE_LTSSM_APP_DLY2_EN		BIT(1)
@@ -84,6 +90,7 @@ struct rockchip_pcie {
 	struct gpio_desc *rst_gpio;
 	struct irq_domain *irq_domain;
 	const struct rockchip_pcie_of_data *data;
+	bool supports_clkreq;
 };
 
 struct rockchip_pcie_of_data {
@@ -199,15 +206,21 @@ static bool rockchip_pcie_link_up(struct dw_pcie *pci)
 	return FIELD_GET(PCIE_LINKUP_MASK, val) == PCIE_LINKUP;
 }
 
-/*
- * See e.g. section '11.6.6.4 L1 Substate' in the RK3588 TRM V1.0 for the steps
- * needed to support L1 substates. Currently, not a single rockchip platform
- * performs these steps, so disable L1 substates until there is proper support.
- */
-static void rockchip_pcie_disable_l1sub(struct dw_pcie *pci)
+static void rockchip_pcie_enable_l1sub(struct dw_pcie *pci)
 {
+	struct rockchip_pcie *rockchip = to_rockchip_pcie(pci);
 	u32 cap, l1subcap;
 
+	/* Enable L1 substates if CLKREQ# is properly connected */
+	if (rockchip->supports_clkreq) {
+		/* Ready to have reference clock removed */
+		rockchip_pcie_writel_apb(rockchip, PCIE_CLKREQ_READY, PCIE_CLIENT_POWER);
+		return;
+	}
+
+	/* Otherwise, pull down CLKREQ# and disable L1 substates */
+	rockchip_pcie_writel_apb(rockchip, PCIE_CLKREQ_PULL_DOWN | PCIE_CLKREQ_NOT_READY,
+				 PCIE_CLIENT_POWER);
 	cap = dw_pcie_find_ext_capability(pci, PCI_EXT_CAP_ID_L1SS);
 	if (cap) {
 		l1subcap = dw_pcie_readl_dbi(pci, cap + PCI_L1SS_CAP);
@@ -282,7 +295,7 @@ static int rockchip_pcie_host_init(struct dw_pcie_rp *pp)
 	irq_set_chained_handler_and_data(irq, rockchip_pcie_intx_handler,
 					 rockchip);
 
-	rockchip_pcie_disable_l1sub(pci);
+	rockchip_pcie_enable_l1sub(pci);
 	rockchip_pcie_enable_l0s(pci);
 
 	return 0;
@@ -320,7 +333,7 @@ static void rockchip_pcie_ep_init(struct dw_pcie_ep *ep)
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 	enum pci_barno bar;
 
-	rockchip_pcie_disable_l1sub(pci);
+	rockchip_pcie_enable_l1sub(pci);
 	rockchip_pcie_enable_l0s(pci);
 	rockchip_pcie_ep_hide_broken_ats_cap_rk3588(ep);
 
@@ -432,6 +445,8 @@ static int rockchip_pcie_resource_get(struct platform_device *pdev,
 		return dev_err_probe(&pdev->dev, PTR_ERR(rockchip->rst),
 				     "failed to get reset lines\n");
 
+	rockchip->supports_clkreq = of_pci_clkreq_present(pdev->dev.of_node);
+
 	return 0;
 }
 
-- 
2.43.0